Chronic stress mediators act synergistically on colonic nociceptive mouse dorsal root ganglia neurons to increase excitability F. OCHOA-CORTES,* , # R. GUERRERO–ALBA,* , # E. E. VALDEZ-MORALES,*, † I. SPREADBURY,* C. BARAJAS-LOPEZ, † M. CASTRO, ‡, §, ¶ J. BERTRAND, ‡, §, ¶ N. CENAC, ‡, §, ¶ N. VERGNOLLE‡, §, ¶ & S. J. VANNER* *Gastrointestinal Diseases Research Unit, Kingston General Hospital, Queen’s University School of Medicine, Kingston, ON, Canada †Instituto Potosino de Investigaci on Cient  ıfica y Tecnol ogica (IPICYT), San Luis Potos  ı, M exico ‡INSERM, U1043, Toulouse, France §Universit e de Toulouse, Universit e Paul Sabatier, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France ¶CNRS, U5282, Toulouse, France Key Messages • Stress hormones directly enhance the intrinsic excitability of DRG neurons, which may combine with organ- specific pathological changes to exacerbate pain in conditions such as IBS. • This study sought to find whether changes in colonic nociception seen with water-avoidance stress (WAS) could also be produced at the DRG level by direct action of stress hormones. • Mice either underwent WAS, or their DRG neurons were exposed overnight to epinephrine and/or corticoste- rone. Colonic DRG neurons were patch clamped, visceromotor reflexes (VMRs) to colorectal distension recorded, and parallel molecular studies conducted. • Chronic exposure to epinephrine and corticosterone synergistically sensitized mouse colonic DRG neurons. Expression of Na v 1.7 and b 2 adrenoceptors was also enhanced by stress hormones. Abstract Background Stress hormones can signal to colonic dorsal root ganglia (DRG) neurons and may play a role in sustained hyperexcitability of nociceptors. Methods Mouse DRG neurons were exposed overnight to epinephrine (Epi) 5 nM and/or corticosterone (Cort) 1 lM or prior water-avoidance stress. Patch clamp recordings, visceromotor reflexes (VMRs) and molecu- lar studies were conducted. Key Results Water-avoid- ance stress induced neuronal hyperexcitability. Incubation of DRG neurons in both Cort and Epi (but neither alone) induced hyperexcitability (rheo- base decreased 51%, p < 0.05; action potential dis- charge increased 95%, p < 0.01); this was blocked by antagonists of the b 2 adrenoreceptor (butoxamine, But) and Cort receptor (mifepristone) in combination or alone. Stress hormones enhanced voltage-gated Na v 1.7 currents (p < 0.05) and suppressed I A (p < 0.0001) and I K+ (p < 0.05) currents. Furthermore, stress hormones increased DRG b 2 adrenoreceptor mRNA (59%, p = 0.007) and protein (125%, p < 0.05), also Nav 1.7 transcript (45%, p = 0.004) and protein (114%, p = 0.002). In whole-animal studies, the WAS hyperexcitability of DRG neurons was blocked by antagonists of the b 2 and glucocorticoid receptors (GCR) but together they paradoxically increased VMRs to colorectal balloon distension. Conclusions & Inferences Stress mediators Epi and Cort activate b 2 and GCR on DRG neurons which synergistically Address for Correspondence Dr Stephen J. Vanner, Kingston General Hospital, Gastrointestinal Disease Research Unit, 78 Stuart St. K7L 2V7, Kingston, ON, Canada. Tel: 613 549 6666 ext 6518; fax: 613 548 2426; e-mail: vanners@hdh.kari.net # Co-first authors. Received: 25 July 2013 Accepted for publication: 1 November 2013 © 2013 John Wiley & Sons Ltd 1 Neurogastroenterol Motil (2013) doi: 10.1111/nmo.12268 Neurogastroenterology & Motility